Problem: Evaluate the following expression when $x = 5$ and $y = 1$. $8$ $x$ $ + 7$ $y$ $ - 7$
Solution: Substitute $5$ for ${x}$ and $1$ for ${y}$ $ = 8{(5)} + 7{(1)} - 7 $ $ = 40 + 7 - 7 $ $ = 40$